linux-kernel - Re: [PATCH v5 1/4] x86/boot: Wrap up the SRAT traversing code into subtable

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Date:   Thu, 12 Dec 2019 21:18:51 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Masayoshi Mizuma <msys.mizuma@...il.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Baoquan He <bhe@...hat.com>,
        Masayoshi Mizuma <m.mizuma@...fujitsu.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 1/4] x86/boot: Wrap up the SRAT traversing code into
 subtable_parse()

On Fri, Nov 15, 2019 at 09:49:14AM -0500, Masayoshi Mizuma wrote:
> From: Masayoshi Mizuma <m.mizuma@...fujitsu.com>
> 
> Wrap up the SRAT traversing code into subtable_parse().

Why?

> 
> Reviewed-by: Baoquan He <bhe@...hat.com>
> Signed-off-by: Masayoshi Mizuma <m.mizuma@...fujitsu.com>
> ---
>  arch/x86/boot/compressed/acpi.c | 21 ++++++++++++++-------
>  1 file changed, 14 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/x86/boot/compressed/acpi.c b/arch/x86/boot/compressed/acpi.c
> index 25019d42ae93..a0f81438a0fd 100644
> --- a/arch/x86/boot/compressed/acpi.c
> +++ b/arch/x86/boot/compressed/acpi.c
> @@ -362,6 +362,19 @@ static unsigned long get_acpi_srat_table(void)
>  	return 0;
>  }
>  
> +static void subtable_parse(struct acpi_subtable_header *sub_table, int *num)
> +{
> +	struct acpi_srat_mem_affinity *ma;
> +
> +	ma = (struct acpi_srat_mem_affinity *)sub_table;
> +
> +	if (!(ma->flags & ACPI_SRAT_MEM_HOT_PLUGGABLE) && ma->length) {
> +		immovable_mem[*num].start = ma->base_address;
> +		immovable_mem[*num].size = ma->length;
> +		(*num)++;
> +	}
> +}
> +
>  /**
>   * count_immovable_mem_regions - Parse SRAT and cache the immovable
>   * memory regions into the immovable_mem array.
> @@ -395,14 +408,8 @@ int count_immovable_mem_regions(void)
>  	while (table + sizeof(struct acpi_subtable_header) < table_end) {
>  		sub_table = (struct acpi_subtable_header *)table;
>  		if (sub_table->type == ACPI_SRAT_TYPE_MEMORY_AFFINITY) {

So this is checking for the table type being something but calling a
function which looks generic, at least judging by the name.

And that generic function is a function why exactly? It beats me. And
the input/output argument @num is actually begging for this to *not* be
a function at all.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette